Piston



M. S. NAPIER.

PISTON.

APPLICATION FILED OCT. 27, 1920.

1,403,560. Patented Jan. 17, 1922.,-

UNITED STATES MONTAGUE STANLEY NAPIER, OF CANNES, FRANCE.

PISTON.

Specification of Letters'latent. Patented J an, 17, 1922,

Application filed October 27, 1920. Serial No. 419,959.

To aZZ whom it may concern:

Be it known that I, MONTAGUE STANLEY NAPIER, a subject of the King of England, and residing at Cannes, Alpes Maritimes, in France, have invented certain new and useful Improvements in Pistons, of which the following is a specification.

This invention relates to pistons more particularly pistons intended for use in internal combustion engines which are formed wholly or as to'their skirts of aluminium or aluminium alloy and has for its object to provide a construction which will obviate that movement of the piston against the walls of the cylinder which is commonly re ferred to as Fslap or tap.

Where the piston is constructed of the same metal as is employed in the formation of the cylinder within which the piston is to move the occurrence of piston slap is avoided by allowing only a small clearance between the exterior of the piston and the inner wall of the cylinder. In the case of a piston constructed of aluminium or aluminium alloy or where the piston skirt is formed of this metal in the usual type of piston it is impossible to make the clearance between the piston and cylinder so small as to prevent slap from taking place owing to the difference in the coefiicients of expansion of the aluminium or aluminium alloy and of the steel cylinder. Slap is considered to be due to the movement of the skirt of the piston against the walls of the cylinder while the head of the piston is prevented from such movement by the piston rings. It is apparent that the above mentioned defect may be overcome if the expansion of the skirt can be regulated to conform with the expansion of the cylinder. This end is attained by the present construction.

According to this invention-the skirt of the piston is slit longitudinally or similarly formed and the minimum necessary clearancebetween the skirt and cylinder is maintained by means of two complete or ,unbroken rings each of which is formed of a metal which has a coefiicient of expansion different from that of the metal of the skirt andsubstantially the same as the coefficient of the metal of which the cylinder is formed The aluminium or aluminium alloy skirt is slit in several places longitudinally'fora substantial part of its length and the two complete rings which are both formed of the same metal having the desired co-eflicient of expansion are disposed within the skirt and fixed thereto toward its outer endbut so that the rings will not be in contact with the the skirt. The coefiicient of expansion of the metal of which the rings are formed is such that the diameter of that part of the skirt which lies outside of or around the rings will be determined by the expansion of the rings which will correspond with the expansion of the cylinder sothat only the clearance necessary to permit of the desired sliding fit of the piston within the cylinder will be maintained. e

The invention may be carried out in various ways but the accompanying drawing which is a longitudinal sectional elevation of one construction of the improved piston illustrates by way of example a formation that may be adopted in practice.

The piston comprises a head A and a skirt B formed integral therewith and having these cuts being conveniently four in num-- her and disposed at equal distances apart around the skirt.

The employment of a single ring of metal having a coefficient of expansion different from that of the metal of which the piston skirt is formed comprises thesubject matter of the present applicants companion application for. United States Letters Patent Serial No. 419,715, filed October 26, 1920. In that case if the divided parts of the skirt are rivetted or otherwise rigidly connected to the ring in more than oneplace distortion of the skirt is liable to occur in some instances. This is avoided in the present invention by employing two continuous un broken metal ring members E and F. Each of these rings is preferably of less width than the single ring if it were used and the two rings are conveniently formed similar as ring which has been divide into equal porflange such as E or F.

tions by a cut taken in a plane at right angles to the peripheral surface of the ring. It is desirable to provide each ring with an inwardly directed flange E F and the two rings are disposedwithin the end of the skirt B close together but not quite in contact and with the one flange E at or adjacent to the end of the skirt. The ring F is arranged with its flanged edge F remote from the adjacent edge of the ring E as shown in the drawing.

Both rings are connected to the divided parts of the skirt B by a series of rivets G and H the rivets G which pass through the ring E being staggered in relation to the rivets H which pass through the ring F. The ring E is connected by only a single rivet G to each part of the skirt B and this rivet is located toward one edge of each part. Similarly the ring F is connected by only a single rivet to each part of the skirt B but each of these rivets is disposed toward that edge of each part of the skirt which is opposite to that edge near which lies the rivet G connecting that part of the skirt to the ring E. The result of this method of connecting the two rings to the several parts of the skirt B is that on expansion of the skirt the two rings will tend to rotate inopposite directions. In some instances it may be preferable to sub-divide the skirt into a greater number of parts each of which is connected to a single ring in one place only so that one half of the parts of the skirt will be thus connected to the one ring while the remaining portions of the skirt will be connected to the other ring.

With the above described construction the expansion of the skirt is controlled or determined by the expansion of the rings E and F which are conveniently constructed of the same -metal as is employed in the construction of the cylinder J within which the piston is to be employed, as for example cast iron or steel. Bronze or other suitable metal may, however, be employed in the formation of the rings. Since the rings will expand in substantially the same way and to the same extent as the cylinder J the aluminium skirt B of the piston will have its external diameter miaintained substantially constant in relation to the diameter of the cylinder. Thus the advantage of an aluminium bearing surface is maintained without the disadvantage which results from the aluminium or aluminium alloy having a coefficient of expansion different from that of the metal of which the cylinder is formed.

The dimensions and form of each of the rings E and F may vary as found desirable and if preferred each of these rings or one of them may be formed flat and without a struction may be modified as desired and the invention may be applied to pistons of The details of convarious types and either where the piston is formed wholly of aluminium or aluminium alloy or where the skirt is formed of this metal and is attached to a head formed of steel, iron or other metal.

What I claim as my invention and desire to secure by Letters Patent is 1. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, two continuous unbroken metal ring members both formed of a metal having a coeflicient of expansion which is different from that of the met-al'of which the skirt is formed, and means whereby the ring members are attached to the divided parts of the skirt adjacent to the outer end of the latter, the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially con stant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

2. In a trunk piston the combination of a head, a skirt formed integral with the head having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, two continuous unbroken metal ring members both formed of a metal having a coeflicient of expansion which is different from that of the metal of which the.

the divided parts of the skirt adjacent to the outer end of the latter, the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

3. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length towards the piston head, two continuous unbroken metal ring members which are formed similar each having a thickening at one edge on its inner side and both members being formed of a metal having a coefficient of expansion which is different from that of the metal of which the skirt is formed, and means whereby the ring members are attached to the divided parts ofthe skirt adjacent to the outer end of the latter, the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will ing longitudinally from its outer end for a substantial part of its length towards the piston head, a continuous unbroken metal ring member which is placed within the skirt towards its outer end and lies in contact with the inner -wall of the divided parts of the skirt, a second and similar continuous unbroken metal ring member which is placed within the skirt adjacent to but on the inner side of the first ring member and not in contact therewith, both ring members being formed'of a metal having a coefficient of expansion which is different from that of the metal of which the skirt is formed, and means whereby the ring members are separately attached to the divided parts of the skirt, the ring members being operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

5. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length towards the piston head, two continuous unbroken metal ring members formed of a metal having'a coefficient of expansion which is different from that of the metal of which the skirt is formed, and rivets extending through the ring members and the divided parts of the skirt so as to rigidly connect each ring mem her to the skirt, the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

6. In a trunk piston the combination of a skirt having in it a plurality of slitsextending longitudinally from its outer end for a substantial part of its length towards the piston head, two continuous unbroken metal ring members each having a smooth periphery adapted to lie within the skirt against its inner wall and each having at one edge -a thickening constituting an inwardly directed flange, both ring members being formed similar and. of a metal having a coeflicient of expansion which is different from that of the metal of which the skirt is formed, and means whereby the ring members are attached to the divided parts of the skirt adjacent to the outer end-of the latter, the ring members being soformed and-posi- .tioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially constant the-minimum necessary clearance between the skirt and the cylinder wall as set forth.

' 7. In a trunk piston the combination of a skirt having in it a plurality'of slits extending longitudinally from its outer end for a substantial part of its length toward the pis-' ton head, two continuous unbroken metal ring members formed of a metal having a coefiicient of expansion which is different from that of the metal of which the skirt is formed, rivets extending, through one of the ring members and each of the divided parts of the skirt at a point situated adjacent to one longitudinal edge of each divided part, and rivets extending through the second ring member and each of the divided parts of the skirt at a point situated adjacent to that longitudinal edge of each part of the .skirt which is opposite to that edge near to which the first ring is attached, the rivets serving to rigidly connect both ring members to the skirt and the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

8. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, acontinuous unbroken metal ring member which is placed within the skirt toward its outer end and lies in contact with the inner wall of the divided parts of the skirt, a second and similar continuous unbroken metal ring member which is placed within the skirt adjacent to but on the inner side of the first ring member and not in contact therewith, both ringmembers being formed of a metal having a coefficient of expansion which is different from that of the metal of which the skirt is formed, rivets extending through the first ring member and each of the divided parts of the skirt at a which the piston is used but will be opera-.

tive to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

9. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, two continuous unbroken metal ring members formed of a metal having a coefficient of expansion which is'different from that of the metal of which the skirt is formed, and rivets extending through the ring members and the divided parts of the skirt so as to rigidly connect each ring member to each part of the skirt the rivets which pass through the one ring member being disposed so as to alternate with the rivets which pass through the secondri ng member, the ring members being so formed and positioned in the skirt that they will not be in contact with the wall of the cylinder in which the piston is used but will be operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

10. In a trunk piston the combination of a skirt having in it a plurality of slits -extending longitudinally from its outer end for a substantial part of its length toward the piston head, a continuous unbroken metal ring member which has at one edge a thickening constituting an inwardly directed flange the periphery of the member lying in contact with the inner wall of the divided parts of the skirt and being placed within the skirt toward its outer end with the flanged edge adjacent to the end of the skirt, a second and'similar continuous unbroken metal I ting member which is placed within flee skirt adjacent to but on the inner side of the first ring member and not in contact therewith with its flanged edge remote from the adjacent edge of the first ring member, both ring members being formed of a metal having a coefficient of expansion which is different from that of the metal of which the skirt is formed, and means whereby the ring members are separately attached to the divided parts of the skirt the ring members being operative to maintain substantially constant the minimum necessary clearance betwen the skirt and the cylinder wall as set forth.

11. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, a continuous unbroken metal ring member which has at one edge a thickening constituting an inwardly directed flange the periphery of the member lying in contact with the inner wall of the divided parts of the skirt and being placed within the skirt toward its outer end with the flanged edge adjacent to the end of the skirt, a second and similar continuous unbroken metal ring member which is placed within the skirt adjacent to but on the inner side of the first ring member and not in contact therewith with its flanged edge remote from the'adjacent edge of the first ring member, both ring members being formed of a metal having a coefficient of' expansion which is different from that of the metal of which the skirt is formed, and rivets extending through the ring members and the divided parts of the skirt so as to rigidly connect each ring member to each part of the skirt the rivets which pass through the one ring member being disposed so as to alternate with the rivets which pass through the second ring member, the ring members being operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

12. In a trunk piston the combination of a skirt having in it a plurality of slits extending longitudinally from its outer end for a substantial part of its length toward the piston head, a continuous unbroken metal ring member which has at one edge a thickening constituting an inwardly directed flange the periphery of the member lying in contact with the inner wall of the divided parts of the skirt and being placed within the skirt toward its outer end with the flanged edge adjacent to the end of the skirt, a second and similar continuous unbroken metal ring member which is placed within the skirt adjacent to but on the inner side of the first ring member and not in contact therewith with its flanged edge remote from the adjacent end of the first ring member, both ring members being formed of a metal having 'a coefficient of expansion which is different from that of the metal of which the skirt is formed, rivets extending through one of the ring members and each of the divided parts of the skirt at a point situated adjacent to one longitudinal edge of each divided part, and rivets extending through the secind ring member and each of the divided parts of the skirt at a point situated adjacent to that longitudinal edge of each part of the skirt which is opposite to that edge near to which the first ring is attached, the rivets serving to rigidly connect both ring members to the skirt and the ring members being operative to maintain substantially constant the minimum necessary clearance between the skirt and the cylinder wall as set forth.

In testimony whereof I have signed my name to this specification.

MON TAGUE STANLEY NAPIER. 

